1. Technical Field
The present invention relates to a technique of driving a discharge lamp that lights by discharge between electrodes.
2. Related Art
A high-intensity discharge lamp, such as a high-pressure gas discharge lamp, is used as a light source for an image display device, such as a projector. As a method of making the high-intensity discharge lamp light, an alternating current (AC lamp current) is supplied to the high-intensity discharge lamp. Thus, in order to improve the stability of light arc occurring within a high-intensity discharge lamp when supplying an AC lamp current to make the high-intensity discharge lamp light, JP-T-2004-525496 proposes to supply to the high-intensity discharge lamp an AC lamp current which has an almost constant absolute value and of which a pulse width ratio between a pulse width of a positive pulse and a pulse width of a negative pulse is modulated.
However, even if the high-intensity discharge lamp is made to light by performing pulse width modulation of the AC lamp current, it may be difficult to stabilize the light arc depending on a state of an electrode of the high-intensity discharge lamp, for example, in a case where a discharge electrode has deteriorated. This problem is not limited to the high-intensity discharge lamp but is common in various kinds of discharge lamps that emit light by arc discharge between electrodes.